1. Field of the Invention
This invention relates to a permanent magnetic alloy comprising precious metals and more particularly to a magnetic alloy mainly composed of gold for use in magnetic personal ornaments.
2. Description of the Related Art
It has been known for a long time that magnetism has an effect upon the human body, and since an effect of magnetism for medical purposes was recently confirmed by public agencies, many kinds of magnetic health implements have been commercialized.
In the field of the magnetic health implements, there are objects called magnetic personal ornaments such as magnetic necklaces, magnetic bracelets and magnetic rings. These magnetic ornaments are that small ferrite magnet or rare-earth magnet pieces are enclosed in metallic receptacles and connected in the shape of a chain. Therefore, they are valued as health implements and accessories, but hardly valued as jewelry. In the circumstances, a precious metal magnet is ardently desired which is mainly composed of gold, platinum, silver or the like and capable of constituting a magnetic alloy by itself.
As a precious metal magnet, a platinum (Pt) - cobalt (Co) alloy magnet is known. This is an order-disorder transition type of alloy containing 77% Pt and exhibits very strong magnetic performance (hereinafter the term "percent, %" means a weight percent). However, an alloy containing less than 85% Pt is not publicly approved as a platinum alloy and it is thought that it has little value as jewelry.
On the other hand, as a magnetic alloy containing gold (Au), an alloy comprising Au, nickel (Ni) and iron (Fe) (Japanese unexamined patent application 57-5833) and an alloy comprising Pt, Au and Fe (U.S. Pat. No. 3,591,373) are known.
The former (hereinafter referred to as conventional alloy ANF) is an alloy containing 75% Au (equivalent to 18 Karat), but its coercive force is about 500 oersteds. A general chain-shaped ornament has a disadvantageous shape for magnetizing, and the coercive force of around 500 oersteds is not enough to provide a sufficient remanence. In order to enable the magnetic ornament to produce a medical effect, it is thought necessary for the ornament to have a remanence of at least 500 gausses (G). In order to obtain this value by a general chain-shaped ornament, as will be explained later, a coercive force of at least 1300 to 1500 oersteds (Oe) is required.
On the other hand, the latter alloy is not approved as a gold alloy, because it is mainly composed of Pt and contains less than 50% Au. Unless the alloy contains at least 50% gold (12 Karat), it would have no such commercial value that it can be called gold jewelry.